Light sources of three colors: red, green, and blue are required for laser projectors. A wavelength conversion laser device that generates a second harmonic wave by using laser light in a 1 μm, band as fundamental laser light has been developed as the green one of these light sources. This light source needs to be small because it is mounted in laser projectors. Further, high-power light sources are required for projectors which require high brightness. In addition, low power consumption is required, and it is necessary to make the light sources operate with a high degree of efficiency.
As a method of implementing a wavelength conversion laser device that satisfies the above-mentioned requirements, a mode control waveguide laser device disclosed by, for example, patent reference 1 has been provided conventionally. The mode control waveguide laser device disclosed by patent reference 1 is comprised of a planar laser medium, two clads that sandwiches the laser medium therebetween, and a heat sink joined to one of the clads. The laser medium has a periodic lens effect, and has a laser oscillation in a waveguide mode of the laser medium, and laser oscillations in a plurality of resonator modes which are formed by the periodic lens effect of the laser medium. As a method of generating the lens effect, the reference shows a method of shaping the heat sink in such a way that the heat sink has a periodic comb structure, and making the pumping light be incident upon a region of the laser medium which is not joined to the heat sink, thereby generating a heat distribution in the laser medium to generate a refractive index distribution.
Further, as a method for providing high power, a solid state laser pumping module disclosed by patent reference 2 has been provided. The solid state laser pumping module disclosed by patent reference 2 is comprised of a solid state laser medium whose front and rear surfaces in a direction of its thickness are set as a laser light incidence surface and an exhaust heat surface, respectively, and an undoped medium optically joined to the laser light incidence surface of the solid state laser medium. The reference shows a structure in which a total reflection film that reflects laser light propagating through the solid state laser medium is disposed on the exhaust heat surface of the solid state laser medium and an antireflection film is disposed on the undoped medium joined to the laser light incidence surface, and pumping light is made to be incident upon a side surface of the thin plate-shaped solid state laser medium so as to oscillate a laser from a direction of the thickness of the solid state laser medium.